This invention relates to a suspension system for a vehicle.
Conventional automobiles and trucks are equipped with soft suspension systems of from 0.8 Hz to 2.0 Hz ride frequency in order to accommodate anticipated road irregularities without discomfort to the passenger. Such soft suspension systems have significant vertical displacement depending on payload changes and thus are not suitable for vehicles which must dock and align vertically with a loading platform over a range of zero to full load. A number of different approaches have been employed to ensure the aligned docking required in some cases to no more than ⅝xe2x80x3 vertical misalignment. For example, small boats at an amusement park ride are drawn up onto submerged rollers to fix the vertical position and prevent rolling during loading. In rail type transit systems complex pneumatic and hydraulic leveling systems are used to ensure vertical alignment between the cab and loading platform over the full range of passenger payload.
It is therefore an object of this invention to provide an improved suspension system for a vehicle.
It is a further object of this invention to provide such an improved suspension system for a vehicle which aligns to loading platforms without need for a complex load leveling system.
It is a further object of this invention to provide such an improved suspension system for a vehicle which accommodates to road surface perturbations, reduces radial transmitted energy such as wheel imbalances or tire out-of-roundness and ensures passenger comfort.
It is a further object of this invention to provide such an improved suspension system for a vehicle which limits vehicle vertical motion and guideway height.
It is a further object of this invention to provide such an improved suspension system for a vehicle which provides compliance on uneven surfaces for better traction.
It is a further object of this invention to provide such an improved suspension system for a vehicle which provides stiffer suspension and more pitch and roll stability.
It is a further object of this invention to provide such an improved suspension system for a vehicle which reduces weight, cost and complexity.
The invention results from the realization that an improved, simpler suspension system for a vehicle which allows vehicle alignment with a loading platform over a wide range of payload while maintaining a safe comfortable ride can be effected by increasing the stiffness of the vehicle sprung mass and using a dynamic absorber mass having a smaller mass than the sprung mass of the vehicle tuned to the ride frequency of the vehicle and mounted for out-of-phase coaxial motion with the vehicle for damping ride frequency perturbations from the vehicle, and the further realization that despite the increased stiffness of the suspension irregularities in the roadway can be accommodated by compliant interconnection of the suspension system and vehicle and/or compliant wheels.
This invention features suspension system for a vehicle including a dynamic absorber mass having a mass smaller than the sprung mass of the vehicle, and a spring system supporting the dynamic absorber mass for out-of-phase coaxial motion with the vehicle and tuned to the ride frequency of the vehicle for damping ride frequency perturbations from the vehicle.
In a preferred embodiment the dynamic absorber mass may be substantially smaller than the sprung mass of the vehicle. It may be 5-15% of the spring mass of the vehicle and in one case may be 10% of the sprung mass of the vehicle. The sprung mass may include the drive system of the vehicle. The spring system may include a plurality of springs interconnected between the vehicle and dynamic absorber mass. The springs may include air bags. The ride frequency may be approximately 3.9 Hz. The suspension system may include a pair of wheels and it may include an axle interconnecting the wheels, two suspension arms connected to the axle, one proximate each wheel, each suspension arm including two spaced links and two pairs of compliant members for interconnecting each of the links of each of the suspension arms to the vehicle for maintaining traction between the wheels and road and accommodating for uneven surfaces of the road. The wheels may include compliant tires for maintaining traction between the wheels and road and accommodating for uneven surfaces of the road. The tires may be pneumatic tires.
The invention also features a vertical suspension system for a vehicle including a dynamic absorber mass having a mass smaller than that of the sprung mass of the vehicle and a spring system supporting the dynamic absorber mass for out-of-phase coaxial motion of the vehicle and tuned to the ride frequency of the vehicle for damping ride frequency perturbations from the vehicle. There are two pairs of wheels, an axle interconnecting each pair of wheels, two pairs of suspension arms connected to the axles one proximate each wheel, each suspension arm including two spaced links and four pairs of compliant members for interconnecting each of the links of the suspension arms to the vehicle for maintaining traction between the wheels and road and accommodating for uneven surfaces of the road. The wheels may include compliant tires and the tires may be pneumatic tires.